One known type of fire collar comprises a metal collar having a liner of an intumescent material which is adapted to be fastened to a barrier, for example, a concrete wall or floor, around a conduit penetrating the barrier. In the event of a fire on one side of the barrier, the intumescent material expands upon its temperature reaching a predetermined level which in turn forces the conduit to collapse or pinches it off thereby inhibiting the spread of fire from one side of the barrier to the other. Examples of such fire collars are described in U.S. Pat. Nos. 058,346 and 347,767. Another form of fire collar relies on the heat from the fire to melt the conduit adjacent the point of penetration and cause the intumescent material to expand across the void left by the melted conduit thereby closing it.
One problem with prior art fire collars is that the time taken for the intumescent material to seal off the void left by a melted conduit can be too long in rapidly advancing fires which may result in fire or poisonous gases penetrating the barrier. That problem has been significantly reduced by the fire collar described in International Patent application No. PCT/AU2004/000143 (International Publication No. WO 2004/072530) by the present applicant. The fire collar described in that application has two opposed torsion springs and a sleeve of intumescent material mounted in a frame such that the frame can be mounted to a barrier and the sleeve fitted about a conduit passing through the barrier whereby the tail of each spring is adapted to engage with the sleeve which in turn engages with the conduit in response to fusing of respective retaining links holding the spring tails in the loaded position. While that fire collar is effective in use, it is more expensive to produce than is desirable.